Oxygen concentration and method

Abstract

An oxygen concentrator is for generating a flow of oxygen by electrolysis of atmospheric humidity. It comprises a cathode ( 24 ) and an anode ( 26 ) contacting opposite sides of a proton-conducting membrane ( 12 ). A catalytic apparatus ( 14 ) comprises a diffusion layer ( 28 ) which spaces a catalyst ( 30 ) from the cathode. The cathode and the catalytic apparatus are contained within a cathode chamber which comprises a ventilation means ( 44 ) for allowing a controlled flow of air to the catalyst. In operation water is electrolysed at the anode and hydrogen generated at the cathode flows through the diffusion layer to the catalyst, where it reacts with atmospheric oxygen to form water which flows back to the proton-conducting membrane for further electrolysis.

1 . An oxygen concentrator comprising;
 a proton-conducting membrane;   a cathode contacting a first side of the membrane;   an anode contacting a second side of the membrane;   a catalytic apparatus comprising a catalyst and a diffusion layer, the diffusion layer spacing the catalyst from the cathode; and   a housing defining a cathode chamber, the catalytic apparatus being contained within the cathode chamber and the housing comprising a ventilation means for allowing air to flow to the catalyst.   
     
     
         2 . An oxygen concentrator according to  claim 1 , in which the ventilation means is arranged to control the flow of air into or through the cathode chamber. 
     
     
         3 . An oxygen concentrator according to  claim 1  or  2 , in which the ventilation means allows ventilation of the cathode chamber between predetermined upper and/or lower limits. 
     
     
         4 . An oxygen concentrator according to  claim 3 , in which ventilation above the predetermined lower limit allows sufficient atmospheric oxygen to reach the catalyst to react with more than 90%, preferably more than 95% and particularly preferably more than 99%, of hydrogen generated at the cathode during use of the concentrator. 
     
     
         5 . An oxygen concentrator according to  claim 3  or  4 , in which ventilation below the predetermined upper limit allows less than 15%, preferably less than 5%, and particularly preferably less than 1%, of water generated at the catalyst by reaction of hydrogen with atmospheric oxygen to be carried away from the catalyst by the ventilating airflow. 
     
     
         6 . An oxygen concentrator according to  claim 3 ,  4 , or  5 , in which ventilation below the predetermined upper limit allows more than 85%, preferably more than 95%, and particularly preferably more than 99%, of water generated by reaction of hydrogen with atmospheric oxygen at the catalyst to pass through the diffusion layer to the cathode and the proton-conducting membrane. 
     
     
         7 . An oxygen concentrator according to any preceding claim, in which the ventilation means comprises one or more vents defined through a wall of the housing. 
     
     
         8 . An oxygen concentrator according to any preceding claim, in which the area of the catalyst and of the cathode are between 150 mm 2  and 2000 mm 2 , preferably between 300 mm 2  and 1000 mm 2 , and particularly preferably between 400 mm 2  and 600 mm 2 . 
     
     
         9 . An oxygen concentrator according to any preceding claim, in which the catalyst is substantially planar, and the cathode chamber has a depth, measured perpendicular to the plane of the catalyst, of between 0.4 mm and 10 mm, preferably between 0.5 mm and 7 mm, and particularly preferably between 0.6 mm and 3 mm. 
     
     
         10 . An oxygen concentrator according to any preceding claim, in which the catalyst is substantially planar and has a lateral dimension, and in which the cathode chamber has a depth, measured perpendicular to the plane of the catalyst, of between 0.1 and 0.015 times, and preferably of between 0.04 and 0.02 times, the lateral dimension. 
     
     
         11 . An oxygen concentrator according to any preceding claim, in which the catalyst has a lateral dimension of between 10 mm and 50 mm. 
     
     
         12 . An oxygen concentrator according to any preceding claim, in which the ventilation means comprises one or more vents defined through a wall of the housing and in which the total area of the vent or vents is between 7 mm 2  and 80 mm 2 , preferably between 10 mm 2  and 40 mm 2  and particularly preferably between 12 mm 2  and 20 mm 2 . 
     
     
         13 . An oxygen concentrator according to any preceding claim, in which the ventilation means comprises one or more vents defined through a wall of the housing and in which the area of the catalyst is between 10 and 70 times, preferably between 25 and 55 times, and particularly preferably between 30 and 45 times, the total area of the vent or vents. 
     
     
         14 . An oxygen concentrator according to any preceding claim in which the ventilation means comprises one or more vents defined through a wall of the housing and in which the area of the cathode is between 10 and 70 times, preferably between 25 and 55 times, and particularly preferably between 30 and 45 times, the total area of the vent or vents. 
     
     
         15 . An oxygen concentrator according to any preceding claim, for operation at a current density between 50 Am −2  and 250 Am −2 , preferably between 75 Am −2  and 200 Am −2  and particularly preferably between 100 Am −2  and 150 Am −2 . 
     
     
         16 . An oxygen concentrator according to any preceding claim, for operation at a voltage of between 0.75V and 2V, preferably between 1V and 1.5V, and particularly preferably about 1.2V. 
     
     
         17 . An oxygen concentrator according to any of  claims 1  to  15 , for operation at a voltage of between 0.75V and 2V, preferably between 0.8V and 1.2V, and particularly preferably at about 1.0V. 
     
     
         18 . An oxygen concentrator according to any preceding claim, for producing a flow of oxygen gas from the anode of less than 30 ml/hour (measured at atmospheric or ambient pressure) for each 500 mm 2  of the area of the anode. 
     
     
         19 . An oxygen concentrator according to any preceding claim, in which the cathode and/or the anode are in the form of layers coated onto opposite sides of the proton-conducting membrane. 
     
     
         20 . An oxygen concentrator according to any preceding claim, in which the catalyst is in the form of a layer coated onto the diffusion layer. 
     
     
         21 . An oxygen concentrator according to  claim 1 ,  19  or  20 , in which the catalyst, the diffusion layer, the cathode, the proton-conducting membrane and the anode are in the form of two or more layers pressed together. 
     
     
         22 . An oxygen concentrator according to  claim 21 , in which the layers are pressed together between a cathode-side conducting sheet and an anode-side conducting sheet for the supply of electric current to the layers. 
     
     
         23 . An oxygen concentrator according to  claim 21  or  22 , in which a pressure of more than 0.5 MPa, preferably more than 0.8 MPa, and particularly preferably more than 0.9 MPa is applied to press the layers together. 
     
     
         24 . An oxygen concentrator according to any preceding claim, in which the catalyst, the diffusion layer, the cathode, the proton-conducting membrane and the anode area in the form of two or more layers pressed together by a pressure which is applied by retaining the layers within the housing, stacked together with a compressed layer of a compressible, preferably resilient, material. 
     
     
         25 . An oxygen concentrator according to any preceding claim, in which a continuous oxygen flow of at least 24 l/hr/m 2  of the area of the catalyst can be produced, measured at NTP, when a constant current density is applied to the oxygen concentrator in air of equal to or greater than 35% relative humidity. 
     
     
         26 . An oxygen concentrator according to  claim 25 , in which the constant current density is less than 150 Am −2  or 120 Am 2 , or preferably about 110 Am −2 . 
     
     
         27 . An oxygen concentrator according to any preceding claim, which does not have a water reservoir. 
     
     
         28 . An oxygen supply unit comprising an oxygen concentrator as defined in any preceding claim, a power supply such as a rechargeable battery, and an oxygen outlet coupled to an anode side of the oxygen concentrator. 
     
     
         29 . An oxygen supply unit according to  claim 28 , which is wearable or ambulatory and is couplable to a hyperbaric dressing. 
     
     
         30 . An oxygen supply unit according to  claim 28  or  29 , in which the power supply supplies a predetermined current to the oxygen concentrator and switches to a stand-by condition if the voltage required to drive the predetermined current rises above a predetermined voltage level. 
     
     
         31 . An oxygen supply unit according to  claim 30 , in which the predetermined current corresponds to a current density across the catalyst or the MEA equal to or less than 150 Am −2  or 120 Am −2 , or preferably of about 100 Am −2 . 
     
     
         32 . An oxygen supply unit according to  claim 30  or  31 , in which the predetermined voltage level is 2.0V, or 1.5V, or 1.2V. 
     
     
         33 . A method for concentrating oxygen from air, comprising the steps of;
 providing a cathode and an anode on opposite sides of a proton-conducting membrane, a diffusion layer adjacent to the cathode and a catalyst spaced from the cathode by the diffusion layer;   allowing access of air to the catalyst through a ventilation means;   passing a current between the cathode and the anode to electrolyse water derived from humidity in the air and from the catalyst, to produce hydrogen at the cathode and oxygen at the anode; and   reacting the hydrogen with atmospheric oxygen at the catalyst to produce water, to pass through the diffusion layer to the cathode for further electrolysis;   in which the ventilation means controls the access of air to the catalyst between predetermined upper and lower ventilation rates.   
     
     
         34 . A method according to  claim 33 , for electrolysing water derived only from humidity in the air and from the catalyst. 
     
     
         35 . An oxygen concentrator substantially as described herein with reference to the drawings. 
     
     
         36 . An oxygen supply unit substantially as described herein with reference to the drawings. 
     
     
         37 . A method for concentrating oxygen substantially as described herein with reference to the drawings.